The invention is directed to a process for the production of pyridine and 3-methyl pyridine by catalytic reaction of acrolein and acetaldehyde with ammonia in the gas phase.
It is known that in the reaction of acrolein with ammonia in the gas phase in the presence of catalysts pyridine and 3-methyl pyridine are formed. As catalysts there have been especially used compounds of the elements Al, F and O which additionally contain at least one element of the second, third or fourth groups of the periodic system and which have been treated with oxygen at temperatures of 550.degree. to 1200.degree. C. (German Offenlegungsschrift No. 2,151,417 or corresponding Beschke U.S. Pat. No. 3,898,177) or at least two elements of the second, fourth, fifth or sixth groups of the periodic system (German OS 2,224,160 or corresponding Beschke U.S. Pat. No. 3,960,766), or at least one element of the second main group of the periodic system (German OS 2,239,801 or corresponding Beschke U.S. Pat. No. 3,917,542). It is also known to carry out the reaction in a fluidized bed with the acrolein fed in separately from the ammonia (German OS 2,449,340 and corresponding Beschke U.S. application No. 622,488 filed Oct. 15, 1975). The disadvantage of these processes is that it is not possible to produce pyridine and 3-methyl pyridine in a substantially different molar ratio than 1 to 2.
Furthermore, it is known that the molar ratio of pyridine to 3-methyl pyridine can be adjusted in a wide range at random by varying the ratio of acrolein to acetaldehyde. As catalysts there are used aluminum oxide, silica or their mixtures, in a given case with addition of oxides of additional elements (Hargrave British Pat. No. 963,887) and in a given case containing fluorides (Distillers Netherlands published application No. 6512937) or there can be used as catalysts compounds consisting of B, P and O, in a given case on carriers of aluminum oxide, silica or their mixtures (Campbell British Pat. No. 1,005,984). In these processes the space-time-yields of pyridine and 3-methyl pyridine are small.